ISO 25901-2:2022 — Welding and Allied Processes — Vocabulary — Part 2: Health and Safety

Overview of ISO 25901-2:2022

ISO 25901-2:2022 is the health and safety vocabulary component of the ISO 25901 series on welding and allied processes terminology. This standard defines over 200 specialized terms organized into five thematic categories: general terms, sampling terminology, measurement terminology, equipment terminology, and personal protective equipment (PPE) terminology. The standard is trilingual (English, French, German) with comprehensive alphabetical indexes for cross-referencing.

Welding health and safety is a complex domain requiring precise terminology to ensure consistent understanding across engineering, industrial hygiene, occupational medicine, and regulatory compliance. Inconsistent terminology can lead to miscommunication about hazard levels, inadequate protective measures, and compromised worker safety. This standard addresses that challenge by providing authoritative, consensus-based definitions.

General and Sampling Terminology

The general terms section (3.1) establishes foundational concepts including definitions of welding fume, gases, particulate matter, and exposure scenarios. Key terms include “arc welding fume” defined as the particulate and gaseous byproducts generated during the welding process, and “occupational exposure limit” (OEL) — the maximum concentration of a hazardous substance to which workers may be exposed without adverse health effects over a specified reference period.

The sampling terminology section (3.2) addresses the critical area of how welding fume and gases are collected for analysis. Proper sampling methodology is essential for accurate exposure assessment. The standard defines terms such as “personal sampling” (sampling in the worker’s breathing zone), “static sampling” (area monitoring), “isokinetic sampling” (maintaining equal velocity between sampled air and sampling inlet), and “gravimetric analysis” (determining fume concentration by mass measurement).

An important term in this category is “respirable fraction” — the fraction of airborne particulate matter that penetrates to the alveolar region of the lung. Welding fume particles typically span a wide size range, and the respirable fraction is the portion most relevant to health effects such as pneumoconiosis and pulmonary fibrosis.

Measurement Terminology and Equipment Standards

The measurement terminology section (3.3) defines how welding emissions and worker exposure are quantified. Key terms include “emission rate” (mass of fume generated per unit time or per unit length of weld), “exposure index” (ratio of measured exposure to the occupational exposure limit), and “time-weighted average” (TWA) concentration. The standard distinguishes between short-term exposure limits (STEL), typically measured over 15 minutes, and long-term exposure limits (LTEL), measured over an 8-hour working shift.

The equipment terminology section (3.4) is the largest category, covering ventilation systems, fume extraction devices, and air cleaning technology. The standard defines terms for “local exhaust ventilation” (LEV), “capture velocity,” “transport velocity,” “high-efficiency particulate air (HEPA) filter,” and “activated carbon filter.” The section also covers source extraction systems including “fume extraction gun” (welding gun with integrated fume extraction), “on-gun extraction,” and “mobile fume extractor.”

Personal Protective Equipment Terminology

The PPE terminology section (3.5) covers all protective equipment used in welding operations. The standard defines terms for “welding helmet” (specifying auto-darkening vs. passive filter types), “respiratory protective equipment” (RPE) including “half-mask,” “full-face mask,” “powered air-purifying respirator” (PAPR), and “supplied-air respirator” (SAR).

An important distinction clarified in the standard is between “air-purifying respirator” (which filters contaminants from ambient air) and “atmosphere-supplying respirator” (which provides clean air from an independent source). For welding operations generating highly toxic fume components (e.g., hexavalent chromium from stainless steel welding), atmosphere-supplying respirators may be required when air-purifying devices cannot provide adequate protection.

The standard also defines “protection factor” (PF) and “assigned protection factor” (APF) — quantitative measures of the level of protection provided by different classes of RPE. These terms are essential for occupational hygienists when specifying appropriate respiratory protection for specific welding tasks.

Engineering and Compliance Implications

For welding engineers and safety professionals, ISO 25901-2:2022 provides the linguistic foundation for effective health and safety management. Consistent terminology enables clear communication between welding engineers, industrial hygienists, occupational health physicians, and regulatory authorities. The standard is referenced by numerous other ISO welding standards, making it an essential reference for anyone working with welding process documentation, risk assessments, or safety management systems.

From a compliance perspective, understanding the precise definitions enables organizations to implement appropriate control measures and demonstrate due diligence. For example, correctly distinguishing between “extraction at source” and “general ventilation” can determine whether a company meets regulatory requirements for controlling welding fume exposure.

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